The overall objective of this proposal is to gain further insight into the secretion and action of decidual luteotropin, a prolactin-like hormone secreted by the decidual tissue of pregnant and pseudopregnant rats. The first aim of this study will be to determine whether decidual luteotropin is produced by either or both mesometrial or antimesometrial cells of the decidual tissue, and whether receptors for this hormone are present in a different cell population than that which produces the PRL-like hormone. Mesometrial and antimesometrial regions will be isolated, and their cells will be dispersed. Both PRL receptors and decidual luteotropin content will be determined by radioceptor assay and by immunohistochemistry. The ability of each cell type to produce decidual luteotropin will be investigated. An enriched population of decidual luteotropin-producing cells will be obtained by isopycnic centrifugation on a Percoll density gradient. Because decidual luteotropin production is inhibited when decidual cells are cultured without continuous removal of medium, a system which allows for continuous perifusion of decidual cells in long term culture will be developed. With this culture system, we will determine whether the decidual luteotropin inhibitor differs from the hormone itself and whether this inhibitor is produced by a cell type other than the decidual luteotropin-producing cell. Rat trophoblast cells secrete a placental lactogen at a time when decidual luteotropin production ceases. The possibility of a local placental interaction between decidual luteotropin and placental lactogen will be investigated. We will specifically determine whether decidual luteotropin prevents the neighboring trophoblastic cells from producing placental lactogen until mid-pregnancy. Finally, with the use of a monoclonal antibody developed against decidual luteotropin, we intend to purify the hormone, develop a radioimmunoassay for it and determine, with the use of both the antibody and the purified hormone, the physiological role of decidual luteotropin.